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LASER SYSTEMS AND MATERIALS
Formation of Microporous Diamond Films by Microwave Plasma CVD from a Diamond-Germanium Composite
V. Sedov, A. Martyanov, I. Tiazhelov
Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow Main author email address: sedovvadim@yandex.ru
Microporous diamond films are a new type of material for applications where a high surface area to volume ratio is required: electrochemistry, electronics, high performance liquid chromatography, in the manufacture of 3D ionizing radiation detectors and mechanically strong filters [1-2]. Porosity can also be used as an antireflection layer in diamond optics. In this work, we propose a new method for the formation of microporous diamond films by growing diamond-germanium composite materials with subsequent selective etching of the germanium component (Fig. 1).
Fig. 1. SEM images of a diamond film after etching of germanium crystallites.
Polished single-crystal silicon wafers used as substrates were seeded with detonation nanodiamonds with an average particle size of 5 nm from an aqueous suspension. Then, a primary microcrystalline diamond film was grown by chemical deposition from methane-hydrogen microwave plasma in an ARDIS 100 reactor (2.45 GHz). At the same time, GeH4 germanium was injected into the chamber, which led to nucleation and growth of crystalline germanium grains simultaneously with diamond.
The formation of Ge grains in a diamond matrix occurs at relatively low temperatures of 750 - 800°C, while at higher temperatures of 850 - 950°C the diamond phase dominates the growth and blocks the development of Ge grains due to a higher rate. Using selective etching of the germanium component in a mixture of hydrofluoric and nitric acids, samples of microporous poly- and single-crystal diamond were obtained.
The work was supported by the Russian Science Foundation, Grant No. 21-72-10153.
[1] T. Pikuz. et. al., 3D visualization of XFEL beam focusing properties using LiF crystal X-ray detector, Scientific Reports, vol. 5, pp. 1-10, (2015).
[2] V. Ralchenko, et. al., Diamond-germanium composite films grown by microwave plasma CVD, Carbon, vol. 190, pp. 10-21, (2022).
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